Exam questions Flashcards
Which gems form by metamorphism?
The metamorphic rocks of East Africa produce tanzanite as well as ruby, emerald, alexandrite, and tsavorite, among others
Which gems can crystallize in volcanic rock from gases released by magma
Both red beryl and topaz can crystallize from gases released by magma during the final cooling stages
Which is a key locality for hydrothermal gems?
Ouro Preto, Brazil. Imperial topaz from Brazil and emeralds from Colombia are important hydrothermal gems
From granite, pegmatite gems get exotic elements like
Beryllium, boron, and lithium are the elements commonly found in pegmatites
Heat and pressure transform limestone into
The limestone deposits of Mogok, Myanmar, are converted to marble by heat and pressure.
Kunzite is most often found in association with
Tourmaline, beryl, and kunzite are all found in association with pegmatites.
Myanmar’s famous Mogok ruby deposits were formed by
metamorphic processes.
Synthetic gem materials
are not minerals because they’re grown in a laboratory rather than in the earth
Which gems are cryptocrystalline aggregates?
Chalcedony and turquoise
Crystals that grow in a flux that is highly saturated with the necessary elements tend to be
SMALL. If the flux is very highly saturated with the elements necessary for crystal growth, many small crystals tend to grow
What Gem materials are commonly twinned?
quartz, feldspar, corundum, and spinel
Which element causes the color of both almandine and peridot?
Iron is the element that causes the red in almandine and the yellowish green in peridot
Which components of a transition element’s atoms can produce color in gems?
Electrons are the components of a transition element’s atoms that produce color in gems.
What is the only type of gem that can show pleochroism?
Only doubly refractive gems can show pleochroism.
Which gems can show three pleochroic colors?
tanzanite and andalusite, iolite
Which element does chromium substitute for to cause ruby’s red?
Aluminum
In many blue sapphires, the intervalence charge transfer that causes the color is between
iron and titanium
The hydrothermal growth process is the only method used to produce which synthetic gem?
Quartz
A snakeskin or honeycomb structural pattern is typical of
synthetic opal.
Synthetic turquoise and lapis lazuli is most likely produced by which process?
Ceramic
Which gems are not heat treated
Iolite, rhodolite, and tsavorite
After irradiation, which gem’s color is stable under normal wearing conditions?
Golden beryl
How deep is the color layer that lattice diffusion with titanium or chromium creates in corundum?
0.01 to 0.50 mm
What agent can create a shallow layer of asterism when it’s introduced below the surface of a corundum cabochon by lattice diffusion?
Titanium oxide. Lattice diffusion creates a shallow layer of asterism in corundum by introducing titanium oxide below the surface. After slow cooling over several days, the titanium oxide crystallizes into rutile needles, which cause the asterism
Heat treatment in a reducing environment can
in sapphire
deepen blue color in sapphire
The vast majority of Sri Lankan deposits are in
alluvial gravels
The finest ruby has a pure, vibrant red to
slightly purplish red hue with medium to medium-dark tone and vivid saturation
The earth’s three most abundant elements are oxygen, silicon, and aluminum.
All corundum varieties are made of aluminum oxide, a mixture of aluminum and oxygen.
Corundum can form only
in an environment with low silicon content
The most renowned rubies, like those from Myanmar, Afghanistan, and northern Vietnam, typically forms in marble during __________ formation process?
metamorphic process, when heat and pressure act on existing limestone deposits. The rubies are found in irregularly distributed layers within the surrounding marble
Iron content inhibits fluorescence, so even if a basalt-hosted ruby’s
hue is excellent, it won’t have the fluorescence of a marble-hosted ruby (Marble iron content is low).
Iron-rich rubies often appear _____.
dark
In rubys: Strong iron content reduces fluorescence, while _______
iron content causes highly visible red fluorescence that brightens ruby
color.
low
Typical _____ clarity characteristics include silk (rutile needles), boehmite needles, included crystals, fingerprint inclusions, growth zoning, and color zoning.
ruby
Heating thai/Cambodian rubies at relatively moderate temperatures of 800° to
1250°C (1472-2282°F) in an _______ environment removed the blue
color and produced a more marketable, pure red hue
oxidizing
_________-temperature heat treatment can sometimes improve ruby color by
removing blue or brown secondary colors, but it is difficult to detect.
_________-temperature heat treatment can improve ruby clarity as well as color.
low, high
__________ lattice diffusion is difficult to detect and often requires laboratory
analysis.
Beryllium
_______ has replaced _________ as the source of the majority of the world’s ruby.
Africa, Southeast Asia
The _________ area of Mozambique has emerged as the world’s most important
ruby source.
Montepuez
The most highly valued blue sapphires are _______blue to _______ blue, in
medium to medium-dark tones, with strong to vivid saturation.
velvety blue to violetish blue
The trace elements _____ and _________ cause the blue of sapphire.
iron and titanium
Blue sapphires can originate in basaltic or non-basaltic environments.
Sapphires that originate in ________ are generally richer in iron than sapphires
from _________ sources.
basalt, non-basaltic
Non-basaltic sapphires form under a variety of conditions, primarily
__________. Sources include Myanmar, Kashmir, Sri Lanka, and most Madagascar deposits
metamorphic
Pleochroism in blue sapphire typically appears as a variation between
slightly_________ blue and slightly_________ blue in different crystal
directions.
greenish, violetish
When a sapphire cutter orients the table facet___________ to the optic axis direction, the finished stone’s face-up color displays more of the
preferred violetish blue and less of the greenish blue hue.
perpendicular
Geuda is heated to around 1250°C (2282°F) in a ___________ environment. If the right concentrations of _________ and ________ are present, a uniform fine blue color results, along with considerable improvement in transparency and luster.
reducing, iron and titanium
Heat-treated geuda and_________ make up a significant portion of the commercial quality
blue sapphire market.
dhun
Most fine sapphires over _____ carats are from _________________
100, Sri Lanka
Which gemstone occurs in almost every color?
Tourmaline
What two coloring agents are usually responsible for color change in gemstones?
Chromium and vanadium
Translucent to opaque rough is usually cut as a ____________ as opposed to being faceted
cabochon
Which colored stone variety has cutting challenges due to vulnerable cleavage planes?
Tanzanite has two directions of cleavage
Gems that are usually eye-clean include
spodumene, yellow beryl, and aquamarine
If an emerald weighs 3.50 cts., with a cost of $10,500.00, what is its per-carat price?
$3,000.00
What is the cost of a ruby that weighs 5.76 cts. and has a per-carat price of $5,500.00?
$31,680.00
When you first start to count a large pile of small gems, it’s best to separate them into groups of
5
Differing amounts and combinations of the trace elements iron, titanium, and____________ cause most fancy sapphire colors.
chromium
The trace element_____________ causes sapphire’s color change.
vanadium
The typical corundum color change is from blue/violet in daylight to___________ purple to strongly_____________ purple in incandescent light
violetish, reddish
Stars are usually made up of 2, 3, or____ intersecting bands, resulting in 4, 6, or__ rays. The most common being 6 rays
6, 12
Hematite inclusions cause the asterism in_______ star sapphires.
black. The sapphire’s bodycolor is actually yellow, green, or blue, but the inclusions make it appear dark brown or black.
The sapphire’s________ is actually yellow, green, or blue, but the inclusions make it appear dark brown or black.
bodycolor
_____________ produces what some consider the widest range of fancy sapphire colors
in the world
Sri Lanka
_______________ is a major source of high quality pink sapphire/ruby
Madagascar
_______________ of sapphire can produce padparadscha colors as well as highly saturated yellows and oranges
Beryllium diffusion
Ruby deposits in Thailand and Cambodia are associated with
alkali basalt
The rubies found in the mountains of Tajikistan, Afghanistan, and Pakistan are all ________ hosted
marble
The flame-fusion method for creating synthetic rubies is also known as
the Verneuil method
The most common crystal habit for ruby is the
tabular hexagonal prism, but crystals from some sources can be elongated prisms and bipyramids
Which of the following have inclusions and growth structures that might closely resemble natural rubies?
Flux and hydrothermal synthetics
Blue sapphire’s most common crystal habit is a(n)
spindle-shaped hexagonal pyramid or bipyramid
Regions associated with basalt-related sapphire include Cambodia, Thailand, _________ and ___________
Nigeria, and Australia
Fancy sapphires from Montana tend to be
light in tone
______star sapphires, however, are prone to parting, so they’re usually cut very flat to reduce the risk of damage
Black
Color-change sapphire typically changes from blue or violet to
strongly reddish purple
The best and most expensive star corundum is________-transparent, with just enough silk to create a well-defined star. Too much silk can harm__________ and also lead to poor color, lowering the value of the stone considerably
semi, transparency
After irradiation treatment, the colors of yellow and orange sapphires will be
unstable
___________ diffusion can also create asterism in both natural and synthetic corundum. As the titanium oxide cools, rutile needles form and align with the gem’s crystal axes. The result is a shallow six-rayed star.
Lattice diffusion with____________ can reduce the impact of dark zoning and improve the color in dark blue basalt-related sapphires. In an oxidizing environment, it removes or lightens most of the blue color, but causes a small amount of yellow to appear.
Titanium, beryllium
Geuda sapphires are treated by heating in a ________________ environment
reducing
For maximum brilliance, stones with low refractive index (RI) require
deeper pavilions and steeper pavilion angles than stones of higher RI
The most desirable emerald colors are________ green to green, with strong to vivid saturation and medium to medium-dark tone. “Columbian”
bluish
___________, ____________, and _____________ are the trace elements that influence emerald’s color.
Chromium, vanadium, and iron
Emeralds can occur in either metamorphic or______________ rock, most emeralds are mined in regions with metamorphic-rock environments, where pegmatites intersect with_______. ie Brazil,
sedimentary, schists
cutter orients the table__________ to the crystal’s length, for the bluish green prized instead of yellowish green pleochlorism
perpendicular
Emerald is mined from___________, hard-rock sources, unlike ruby and sapphire, which are found mostly in _____________ deposits
primarily, secondary
Muzo, Coscuez, La Pita, and Chivor are the primary emerald-producing areas in_____________. In __________, the main sources are in the Minas Gerais and Bahia states.
Colombia, Brazil
Three signs that an “emerald” might be glass are ______ ______________, concave surfaces, and rounded facet junctions
gas bubbles
2 methods, _________________ and _______________ are used to grow synthetic emeralds, with ____________ being the primary synthetic emerald growth method.
flux and hydrothermal, hydrothermal
Zambia’s Kagem mine produces an estimated ___ percent of the world’s emerald supply
20%
_____________ ______________ produced a hydrothermal synthetic emerald in the 1960s by depositing a synthetic emerald layer, on faceted beryl seeds
Johann Lechleitner
Which country is the number one supplier to the US in terms of total carats
India
The great majority of emeralds come from Colombia, Zambia, Brazil, _____________ and ______________
Afghanistan and Pakistan
A saltwater cultured whole pearl (oysters) grows from a mantle-tissue piece and a __________ ___________ implanted in a host mollusk’s___________. ie akoya, south sea, tahitian
bead nucleus, gonad
Most freshwater cultured whole pearls (mussels) are grown from mantle-tissue pieces implanted in a host mollusk’s__________
mantle
Most Chinese freshwater cultured pearls are-__________ nucleated (non-beaded).
mantle
The seven Pearl value factors are:
- Size
- Shape
- Color
- Luster ** most important
- ___________ Quality
-__________ Quality
- Matching
Surface, Nacre
Gamma radiation changes cultured pearl color because of its effect on the chemical element____________. This treatment is most frequently used to treat_____________ cultured pearls because they typically contain more manganese than saltwater cultured pearls
manganese, freshwater
Jadeite’s 3 most important qualities are…… The most important being __________
color, transparency, and texture. Color
Jade’es green ranges from a pure green to a__________ bluish or slightly____________ green. Lavender is jadeite’s second most valued color. Lavender jadeite gets its color from trace amounts of_______________
slightly, yellowish. manganese
___________: a rock composed mainly of calcium, magnesium and iron silicate minerals
___________: a Metamorphic rock composed mostly of sodium and aluminum silicate minerals
nephrite, jadeite
Type A jadeite is technically completely natural, but it can be dipped in wax or treated with a surface coating of wax.
Type B jadeite is___________ and impregnated
Type C jadeite is ___________
bleached, dyed
Jade that was dyed as well as impregnated might be called
Type B + C.
Nephrite and jadeite are both extremely tough, but______________ interlocking fibrous
structure makes it more resistant to fracturing
nephrite’s
Nephrite is a rock composed mainly of minerals in the amphibole group, made up of complex minerals with similar structures.
Jadeite’s major component is pyroxene, a complex silicon-containing mineral with a structure unlike amphiboles
Nephrite vs Jadeite
Nephrite forms by metasomatism in various geological settings.
1. forms when dolomite contacts silicon-containing fluids in association with magmatic activities.
2. is produced when serpentinite contacts calcium-rich silicon-containing rocks.
1 is less common, it produces the very popular white nephrite.
Opals occur in both_________ and____________ rocks
sedimentary, volcanic
opal origin dates back between about __ thousand and____ million years.
7, 110
Opal types are often based on
background color/ base color
_____________ command the highest prices of all opal types
Black opals
The most valuable fire opals usually display uniform________-__________ to bright red color
red-orange, “cherry”
What three aspects combine to create an opal’s unique beauty?
Color, pattern, and clarity
* Color—Background color and play-of-color
* Pattern—Arrangement of play-of-color
* Clarity—Transparency and number of inclusions
In opal,__________ is often considered the most desirable play-of-color hue
Red
Maximizing _____________ is an opal cutter’s main goal
play-of-color
Unlike other opal types, the building blocks of red-to-yellow fire opals from Mexico are randomly arranged silica____________ rather than spheres
platelets
The world’s main source of fine-quality black opal is the ________________________ town of Lightning Ridge
New South Wales
The finest amethysts are a strongly saturated, medium-dark to dark_________ purple or purple, with no visible color zoning. AAA, “African” or “Zambian”
reddish
Color zoning is most visible when an amethyst is viewed face-________through its
pavilion on a white background.
down.It’s not as visible face-up.
___________is the world’s major source of commercial-quality amethyst
Brazil. Para in the north, and Rio Grande do Sul South
The finest citrine color is a saturated yellow to_________ orange, free of brownish tints
reddish
There’s only one source of natural ametrine: a deposit in eastern___________, close to the Brazilian border
Bolivia
The finest chrysoprase color is a light to medium___________ green “ golden apple”
yellowish
Treated black chalcedony—known in the trade as __________ ____________—is sold in larger quantities than any other chalcedony variety
black onyx
Quartz varieties differ mostly in the______ of their crystals
size
___________-in-chalcedony is one of the most valuable chalcedony varieties
Chrysocolla
The best tanzanite color is a strongly saturated pure blue or____________ blue
violetish
Gem-quality tanzanite comes from just one place on earth—the__________ area in Tanzania
Merelani
Synthetic ____________ is the most convincing tanzanite imitation to date
forsterite
_____________ chrysoberyl is the finest color-change gem, and the standard against which all other color-change gems are judged
Alexandrite
Fine alexandrite is green to__________ green in daylight/ fluorescent light and red
to_________ red in incandescent light, with medium to medium-dark tone and
moderately strong saturation
bluish, purplish
true milk and honey, where one side of the gem is a semi-transparent to _____________ slightly brownish yellow, and the other a____________ green
translucent, yellowish
The nacre quality classification described as “Nucleus not noticeable, no chalky appearance” is
Acceptable
* Acceptable—Nucleus not noticeable, no chalky appearance
* Nucleus Visible—The cultured pearl shows evidence of its bead nucleus through the nacre
* Chalky Appearance—The cultured pearl has a dull appearance
Heat treatment of jadeite might produce a
brownish orange color
In Myanmar, the center of the jadeite mining district is
Hpakant
Experts think fire opal’s background color is caused by
iron impurities
The color of amethyst results from
color centers caused by natural irradiation acting on trace elements of iron
Tiger’s-eye and hawk’s-eye quartz are______________ aggregates. Their chatoyancy is caused by fibrous structures
microcrystalline
a major source of cat’s-eye chrysoberyl?
Sri lanka
Colombian emeralds are unique because they form
in a sedimentary environment in mineral-rich hydrothermal veins with sedimentary rock
The country that is a major manufacturer of chalcedony cameos and carvings is
Germany
The synthesis method that produces the quartz needed to meet the huge demand in the electronics industry is
hydrothermal
Which of the following is most commonly used to imitate alexandrite?
synth corundum
To best show the cat’s-eye effect, the cutter orients the inclusions
parallel to base/ across the length of the cabochon
What causes the wide variety of colors in topaz
Color centers and traces of chromium
The _________________ area of Brazil is the world’s major commercial source of imperial and red topaz
Ouro Preto
If yellow to reddish brown topaz contains chromium, careful heat treatment can
produce a_____________ color
pink
Morganite is almost always heated, or irradiated first and then heated, to produce or improve the______ color. Is stable.
Red_________ does not respond to heat treatment.
pink, beryl
Red Beryl cut with the table perpendicular to the crystal’s length show a more uniform orange-red hue. For best overall color, that’s the preferred orientation.
Cut with the table parallel to the crystal’s length are more_________ red
purplish
“bixbite” or _______ beryl is the rarest beryl. It’s often a highly saturated, pure red color, raspberry red
red
The US state of___________ is the world’s only known source of red beryl. Wah wah mountains
Utah
Tone and_____________ levels distinguish green beryl from emerald
saturation
Most gem tourmalines are elbaites that form in______________
pegmatites
_________supplies the majority of the world’s gem-quality tourmaline
Brazil, minas gerais
Traces of__________ cause Paraíba tourmaline’s extraordinary colors
copper
Sources in____________ supply the world with most of its large, fine-color peridot.
_________ supplies the world with rough for much of its commercial calibrated
peridot
Myanmar,
Arizona
The most valued lapis contains little or no_________, no calcite, and is an intense, uniform, medium-dark, slightly violetish blue. Known as “Afghan”
pyrite
Lapis treatments are common, but not permanent. Lapis might be dyed, impregnated with wax or plastic, or heated and then________.
dyed
Matrix-free and_____________ turquoise command the highest prices
spiderweb
The southwestern US is the world’s Largest Producer and consistent market of turquoise.
China’s______ Province is the major source of its top color “ sky blue”
Hubei
Feldspar, spodumene, and diopside are A. soft gems and 2. Cleavage in _____ directions, so they require protective settings
two
_____________ are the most widespread minerals on earth
Feldspars
The phenomenal moonstone variety includes all____________ feldspars
adularescent
The finest moonstones possess a colorless, semitransparent to nearly____________ appearance and vivid blue
adularescence
transparent
The most prized labradorite type is “____________,” a phenomenal labradorite with brilliant spectral hues
spectrolite
Small inclusions give sunstone a reddish or___________ sheen, while larger inclusions create glittering reflections
golden
High clarity and lack of treatment make chrome diopside an effective_____________ alternative
emerald
Moonstone’s adularescence is caused by the scattering of light by stacked, alternating mineral layers.
Labradorite’s phenomenal colors are caused by___________ of light reflecting off the gem’s layered structure
interference
The _______ Sea region and the Dominican Republic are amber’s principal sources
Baltic
The most valuable red coral is an intense red that dealers call____________
oxblood
Rhodolite is a mixture of __________ and ____________
pyrope and almandine.
Spessartine is most commonly found in
(mandarin garnet)
pegmatite veins. Unlike many garnets, which are found in metamorphic rocks, spessartine is most often found in pegmatite veins
The most common crystal habit of all garnets is the
All garnets belong to the cubic crystal system, and their most common habit is the dodecahedron
All garnets have essentially the same
crystal structure
In general the most desirable spinel color is
red
_________ causes Malachite’s color and the “Persian” blue Turquoise
copper
The only source of charoite is
The only known commercial source of chrome diopside
russia
Which of the following does turquoise usually form in?
limonite or sandstone
The world’s major source and The finest trade grade of lapis lazuli is
“afghan” Afghanistan
The greenish blue feldspar that has gridlike white streaks and resembles turquoise is
Amazonite
Which of the following three basic chemical elements do all feldspars contain?
Aluminum, oxygen, and silicon
organics shows a structure called “engine turning,” which looks like lines created on a lathe
ivory
The only source of gem-quality benitoite is
California
Jet is an ornamental form of
lignite coal, formed when wooden logs washed out to sea and sank into mud on the sea floor.
Transparent_______ amber is more valuable than ________ amber, which is more valuable than yellow amber
red, golden
Two basic types of gem coral 1.calcareous coral 2. conchiolin coral
__________________ coral is principally calcium carbonate
__________________ coral’s principal ingredient is a protein
Calcareous, conchiolin
2 Types Conchiolin coral colors in jewelry:
Black coral/ king’s/______ coral— the waters off Queensland, Australia, and Hawaii.
Golden coral comes from the waters off Hawaii and Tasmania, Australia
akabar
Pure corundum is colorless because it has a large _________ gap. However, traces of transition elements like chromium,
iron, and titanium cause color through _____________ _____________
band
selective absorption
Heat treatment removes unwanted colors by destroying the color ____________ that cause them
centers
copper colors which gems……
malchite, turquois, paraiba tourmaline,
